Electric charging device for electrophotography

ABSTRACT

Method and apparatus for uniformly charging the surface of a curved insulating member. A carrier member has a plurality of joining members disposed at substantially equal intervals thereon. Each of a plurality of needle electrodes is retained respectively by an associated joining member. When a force of sufficient magnitude is exerted on the needle electrodes, the tips of the electrodes are forced into contact with the member, the tips forming an envelope which conforms to the curved surface of the member. The needle electrodes are subsequently withdrawn to a predetermined position above the surface and an electric discharge potential is applied thereto, whereby a uniform electric charge is deposited on the surface of the insulating member.

United States Patent Takimoto et al.

[15] 3,655,966 [451 Apr. 11, 1972 [541 ELECTRIC CHARGING DEVICE FORELECTROPHOTOGRAPHY [72] Inventors: Masaaki Takimoto; Masamichl Sato; Sa-

toru Honjo, all of Asaka, Japan [58] Field of Search ..250/49.5 R, 49.5TE, 49.5 GC, 250/495 ZC, 49.5 TC; 317/262 A; 355/3, 17

[56] References Cited UNITED STATES PATENTS 2,864,756 12/1958 Rothacker..250/49.5 TC

3,483,374 12/1969 Erben ..250/49.5 TC

Primary Examiner-Archie R. Borchelt Assistant Examiner-C. E. ChurchAttorney-James J. Ralabate, John E. Beck and Irving Keschner [57]ABSTRACT Method and apparatus for uniformly charging the surface of acurved insulating member. A carrier member has a plurality of joiningmembers disposed at substantially equal intervals thereon. Each of aplurality of needle electrodes is retained respectively by an associatedjoining member. When a force of sufficient magnitude is exerted on theneedle electrodes, the tips of the electrodes are forced into contactwith the member, the tips forming an envelope which conforms to thecurved surface of the member. The needle electrodes are subsequentlywithdrawn to a predetermined position above the surface and an electricdischarge potential is applied thereto, whereby a uniform electriccharge is deposited on the surface of the insulating member.

13 Claims, 1 1 Drawing Figures PATENTEDAPR 1 1 m2 SHEET 1 BF 3 I05III.IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII FIG. 2 .i,

S M V TT U E N R N EW O R VKAT 0 WASA T T S T m A KIJ AMN Mam AA MM V YB PATENTEDAPR 11 m2 3,655,966

sum 2 or a Z rzz/ W40 I I EHI I I HHI I I BACKGROUND OF THE INVENTIONThe charging devices heretofore used in charging insulative members suchas those utilized in electrophotography are designed to accomplishelectric charging of electrophotographic sensitive layers in the form offlat or cylindrical members and therefore fail to provide electriccharging for sensitive layers in complicatedly rugged forms. With theadvance ment of electrophotography, electrophotographic sensitive layershave become all the more complicated in shape, making it necessary todevelop an electric charging device usable therewith. Where a givensensitive layer happens to have the shape of corrugated plate, forexample, electric charging made by suing conventional electric chargingdevices enables the portion of the corrugated plate in corresponding toridges of the corrugation to be charged to a higher potential because ofthe smaller distance from the corona discharge electrode and the portioncorresponding to grooves to be charged to lower potential because of thegreater distance from the corona discharge electrode. From the nature ofelectrophotographic equipment, however, it is necessary that the portioncorresponding to ridges and the portion corresponding to grooves becharged to equal potential.

SUMMARY OF THE INVENTION The present invention provides method andapparatus for uniformly charging the surface of a curved insulatingmember. In particular, a carrier member has a plurality of joiningmembers disposed at substantially equal intervals thereon. Each of aplurality of needle electrodes is retained respectively by an associatedjoining member. When a force of sufficient magnitude is exerted on theneedle electrodes, the tips of the electrodes are forced into contactwith the member, the tips forming an envelope which conforms to thecurved surface of the member. The needle electrodes are subsequentlywithdrawn to a predetermined position above the surface and an electricdischarge potential is applied thereto, whereof a uniform electriccharge is deposited on the surface of the insulating member.

It is an object of the present invention to provide method and apparatusfor uniformly charging the surface of a curved insulating member.

It is a further object of the present invention to provide method andapparatus for uniformly charging an electrophotographic sensitive layerformed on the surface of a curved conductive member.

It is still a further object of the present invention to provide methodand apparatus for uniformly charging the surface of a curved insulatingmember wherein a plurality of needle electrodes joined to a carriermember are forced into contact with the insulating surface andsubsequently withdrawn, the tips of the electrodes forming an envelopeconforming to the curved insulating surface.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention as well as other objects and further features thereof,reference is made to the following description which is to be read inconjunction with the accompanying drawing wherein:

FIG. 1 is a schematic sectional view of the electric charging apparatusof the present invention;

FIG. 2 is a sectional view of the apparatus shown in FIG. 1 in the stateassumed when the apparatus is lowered until the tips of the needleelectrodes thereof come into contact with the surface of the curvedplate,

FIG. 3 is a sectional view illustrating the apparatus as elevated fromthe state in FIG. 2 up to a desired position;

FIG. 4 is a sectional view illustrating one mode of returning the needleelectrodes of the apparatus to their original state;

FIG. 5 is a schematic oblique view of another embodiment of theapparatus according to the present invention;

FIGS. 6 (a)-6 (c) are enlarged sectional views illustrating variouspreferred embodiments of the joining member for fixing a needleelectrode on a carrier plate;

FIG. 7 is a partially enlarged sectional view illustrating anotherembodiment of the joining member;

FIG. 8 is a sectional view illustrating an embodiment having anauxiliary carrier plate incorporated for needle electrode parallelism;and

FIG. 9 is a schematic oblique view illustrating an embodiment having acylindrical guard disposed around every other needle electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 represents apparatus forproviding uniform electric charging a curved insulating member. Forexample, an electrophotographic sensitive layer is disposed on thesurface of a curved conductive plate 102 mounted on base 101. Typicalelectrophotographic materials include cadmium sulphide, zinc oxide,selenium, sulphur selenium, etc. Numeral 103 denotes the electriccharging apparatus of the present invention. Numeral 104 denotesneedle-shaped charging electrodes of a fixed length; a multiplicity ofsuch charging electrodes are arranged substantially uniformlytwo-dimensionally. A carrier plate 105 is provided for the needleelectrodes 104, with the joining of the needle electrodes to the carrierplate being accomplished by means of joining members 106. The joiningmembers 106 are either fixed onto the carrier plate 105 or formedinseparably therewith. The needle electrodes 104 are held in position bythe joining members 106 in such way that, when exposed to a force ofsufficient magnitude exerted in the axial direction thereof, they willslide in that direction but otherwise will be prevented from sliding. Inother words, the retaining force of joining members 106 is limitedwithin a certain level, so that, when the retaining force is overcome bya force of sufficient magnitude exerted in the axial direction, thejoining members will allow the needle electrodes to slide. Examples ofjoining member 106 will be described hereinafter with reference to FIGS.6(a)-6(c). FIG. 2 is a view of the electric charging device portion 103of FIG. 1 in the state to be assumed when it has been pushed downward(or the base 101 is pushed upward) until the tips of the needleelectrodes reach the lowermost point of the curved plate 102. Since theneedle electrodes are movable by external force overcoming the retainingforce, or power, of the joining members 106 and ex erted in the axialdirection, those needles electrodes which have reached the elevatedportion of the curved plate are pushed back above the carrier plates105. As shown in FIG. 2, therefore, an envelope 201 is formed by theheads of the needle electrodes conforming to, or in correspondence with,the shape of the curved plate.

When the electric charging apparatus is removed from the surface of thecurved plate (or the base 101 is lowered downward) and brought to a stopat a desired position or height, as illustrated in FIG. 3, the tips ofthese needle electrodes and the curved plate are spaced by asubstantially equal interval and the needle tips contacting the surfaceform an envelope conforming to the shape of the curved plate. When theseneedle electrodes are joined electrically and a high electric potentialis applied between the needle electrodes and the curved plate, coronadischarge is produced from the tips of these needle electrodes thesurface of the curved plate being charged substantially uniformly.According to the present invention, therefore, uniform electric chargingcan be accomplished on any curved member no matter how complex the shapemay be.

When another curved plate is to be charged, a flat plate 401 may bepushed down upon the electric charging apparatus as illustrated in FIG.4 of the electric charging apparatus may be pushed up against the flatplate 401 so as to cause the heads of the needle electrodes to bealigned. In this way, the electric charging apparatus can be broughtback to its original state shown in FIG. 1. For subsequent cycles ofcharging, this procedure has only to be repeated.

The foregoing description presumes a case in which the surface of thecurved plate has a three-dimensionally varied shape. Where the surfaceof the curved plane has a twodimensionally varied shape, namely, whenthe curved plate is something like a corrugated plate, the device ofthis invention becomes much simpler. FIG. 5 is a schematicrepresentation of the apparatus of the invention which is usable in suchcase. For the purpose of electrically charging a corrugated plate 502 onthe base 501, the electric charging apparatus 503 comprises a row ofneedle electrodes 504, a supporting bar 505 and joining members 506.Similarly to the apparatus described hereinabove, the needle electrodesand the joining members are retained by a limited magnitude of force.When the tips of the needle electrodes are so arranged as to conform tothe shape of the corrugated plate 502 and electric potential is appliedthereto while they are moved to scan the surface in the direction of thearrow mark 507 (the direction in which the sectional shape of thecorrugated plate remains unchanged) the surface of the corrugated plateis charged substantially uniformly.

FIG. 6 shows a few specific examples of the joining member. FIG. 6 (0)represents an example utilizing a rubber bushing 603, in which a needleelectrode 601 is retained in the hole of the bushing while the bushingis fixed on the carrier plate 602. When the hole in the rubber piece isgiven a diameter slightly smaller than that of the needle electrode, theelectrode is made to slide by a force of sufficient magnitude applied inthe axial direction of the needle electrode to overcome the retainingforce of rubber bushing 603. FIG. 6 (b) represents an example making useof a leaf spring 613. One end of this leaf spring is fixed on thecarrier plate 602 and the other end holds the needle electrode inposition together with the corresponding end of another leaf spring 613.The object of the invention can be fulfilled by selecting the strengthof the leaf spring suitable. FIG. 6 (0) represents an example utilizingthe resiliency of the carrier plate 602 itself. A portion of the carrierplate is bent as illustrated so as to function as a spring, with theresiliency produced thereby utilized for supporting the needleelectrode. The joining member suffices so long as it has a constructionsuch that the needle electrode is moved by a force of sufficientmagnitude to overcome the retaining force of the joining member. FIG. 7shows another preferred embodiment of the device of the presentinvention. FIG. 7 represents a device so designed that the needleelectrodes can be moved freely only when the envelope formed by the tipsof needle electrodes is arranged to conform to the shape of the curvedplate, while they are immobilized at any other time. The needleelectrode 601 can fall freely by gravitational pull through the guide604 which is provided at one portion of the carrier plate 602. When theelectromagnet 605 is functioning, however, the needle electrode isattracted by the electromagnet and therefore is prevented from falling.When the envelope is desired to be formed, therefore, the electromagnetis not energized, enabling the needle electrode to fall until it reachesthe curved plate. The envelope conforming to the curved plate can beobtained by energizing the electromagnet at the time the needleelectrode reaches the curved plate and then lifting the electriccharging apparatus. Any suitable device which can take the place ofelectromagnet 605 and which produces the same effect as mentioned abovemay be utilized.

Although the carrier plates are maintained horizontally in all theillustrated examples, they may be inclined by a desired angle, ofcourse. This angle is determined by the case with which the surfacebeing charged can be retained.

The needle electrodes 804 joined by joining member 806 to carrier plate805 may be maintained in exact parallelism with one another by utilizingan auxiliary carrier plate 807, as shown in FIG. 8.

The intervals between the needle electrodes are determined by the shapeof the surface to be charged, the distance from the surface for chargingto the tips of the needle electrodes, and the required degree ofuniformity of electric charging and therefore cannot be fixedabsolutely.

Generally speaking, uniform electric charging can be obtained byselecting the intervals such that the shape of individual sections ofthe material falling between two adjacent needle electrodes can benearly approximated by a straight line or a plane.

The individual needle electrodes are maintained at an equal electricpotential. If they are placed too close to one another, therefore, theymay be affected by those positioned in the immediate neighborhood.Accordingly, they may fail to produce equal discharging. To avoid this,a grounded conductor arranged close to each needle electrode may beprovided. According to one conceivable method, charging apparatus 903and curved plate 905 may be arranged to include a cylindrical guard, orshield 908, disposed around every other needle electrode 904 asillustrated in FIG. 9, for example. The guard 908 may be disposed as tobe moved up and down synchronously with the movement of the electrode orit may be fixed at a given height.

Although the member to be charged has been characterized as including anelectrophotographic layer, the present invention may be utilized withequal facility with an electrically insulating layer formed on a curvedsubstrate. For example, a latent electrostatic image may be formed on alayer of plastic formed on a curved substrate.

While the invention has been described with reference to its preferredembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teaching of the inventionwithout departing from its essential teachings.

What is claimed is: l. A method for uniformly charging the surface of acurved insulating member comprising the steps of:

positioning a carrier member having a plurality of joining membersdisposed at substantially equal intervals thereon above said insulatingsurface, a plurality of needle electrodes being retained respectively bymeans of said joining members substantially vertical with reference tothe plane of said carrier member, applying a force of sufficientmagnitude to said needle electrodes to overcome the retaining force ofsaid joining members, whereby said needle electrodes are caused tocontact said insulating surface, the tips of said needle electrodesforming an envelope which conforms to the shape of the insulatingsurface, separating said needle electrodes and said insulating surface apredetermined distance, and

applying an electric discharge potential to said needle electrodeswhereby the corona discharge emitted by said needle electrodes depositssubstantially uniformly on said insulating surface.

2. The method as set forth in claim 1 wherein said insulating membercomprises an electrophotographic layer overlying a conductive substrate.

3. The method as set forth in claim 1 further including the step ofrealigning the tips of said needle electrodes.

4. A method for uniformly charging the surface of a curved insulatingmember comprising the steps of:

positioning a carrier member having a plurality of joining membersdisposed at substantially equal intervals thereon above said insulatingsurface, a plurality of needle electrodes being retained respectively bymeans of said joining members substantially vertical with reference tothe plane of said carrier member,

releasing the retaining force of said joining members on said needleelectrodes, whereby said needle electrodes are caused to contact saidinsulating surface, the tips of said needle electrodes forming anenvelope which conforms to the shape of the insulating surfacereapplying the retaining force of said joining members on said needleelectrodes,

separating said needle electrodes and said insulating surface apredetermined distance, and

applying an electric discharge potential to said needle electrodeswhereby the corona discharge emitted by said needle electrodes depositssubstantially uniformly on said insulating surface.

5. The method as set forth in claim 1 wherein said insulating membercomprises an electrophotographic layer overlying a conductive substrate.

6. Apparatus for uniformly charging the surface of a curved insulatingmember comprising:

a carrier member having a plurality of joining members disposed atsubstantially equal intervals on said carrier member and a plurality ofneedle electrodes retained respectively by said joining memberssubstantially vertical with reference to the plane of said carriermember, said carrier member being positioned above said insulatingsurface, v

means for applying a force to said needle electrodes of sufficientmagnitude to overcome the retaining force of said joining memberswhereby said needle electrodes are caused to contact said insulatingsurface, the tips of said needle electrodes forming an envelope whichconforms to the shape of the insulating surface,

means for separating said needle electrodes and said insulating surfacea predetermined distance, and

means for applying an electric discharge potential to said needleelectrodes, whereby the corona discharge produced by said needleelectrodes deposits substantially uniformly on said insulating surface.

7. The apparatus as set forth in claim 6 wherein said insulating membercomprises an electrophotographic layer overlying a conductive substrate.

8. The apparatus as set forth in claim 6 further including an additionalcarrier member for supporting said needle electrodes, whereby saidneedle electrodes are maintained substantially in parallelism.

9. The apparatus as defined in claim 6 further including means forshielding said needle electrodes from the effect of the dischargeproduced by adjacent needle electrodes.

10. Apparatus for uniformly charging the surface of a curved insulatingmember comprising:

a carrier member having a plurality of joining members disposed atsubstantially equal intervals on said carrier member and a plurality ofneedle electrodes retained respectively by said joining memberssubstantially vertical with reference to the plane of said carriermember, said carrier member being positioned above said insulatingsurface,

means for releasing the retaining force of said joining member on saidneedle electrodes whereby said needle electrodes are caused to contactsaid insulating surface, the tips of said needle electrodes forming anenvelope which conforms to the shape of the insulating surface,

means for reapplying the retaining force of said joining members on saidneedle electrodes,

means for separating said needle electrodes and said insulating surfacea predetermined distance, and

means for applying an electric discharge potential to said needleelectrodes, whereby the corona discharge produced by said needleelectrodes deposits substantially uniformly on said insulating surface.

11. The apparatus as set forth in claim 10 wherein said insulatingmember comprises an electrophotographic layer overlying a conductivesubstrate.

12. The apparatus as set forth in claim 10 further including anadditional carrier member for supporting said needle electrodes, wherebysaid needle electrodes are maintained substantially in parallelism.

13. The apparatus as defined in claim 10 further including means forshielding said needle electrodes from the effect of the dischargeproduced by adjacent needle electrodes.

1. A method for uniformly charging the surface of a curved insulatingmember comprising the steps of: positioning a carrier member having aplurality of joining members disposed at substantially equal intervalsthereon above said insulating surface, a plurality of needle electrodesbeing retained respectively by means of said joining memberssubstantially vertical with reference to the plane of said carriermember, applying a force of sufficient magnitude to Said needleelectrodes to overcome the retaining force of said joining members,whereby said needle electrodes are caused to contact said insulatingsurface, the tips of said needle electrodes forming an envelope whichconforms to the shape of the insulating surface, separating said needleelectrodes and said insulating surface a predetermined distance, andapplying an electric discharge potential to said needle electrodeswhereby the corona discharge emitted by said needle electrodes depositssubstantially uniformly on said insulating surface.
 2. The method as setforth in claim 1 wherein said insulating member comprises anelectrophotographic layer overlying a conductive substrate.
 3. Themethod as set forth in claim 1 further including the step of realigningthe tips of said needle electrodes.
 4. A method for uniformly chargingthe surface of a curved insulating member comprising the steps of:positioning a carrier member having a plurality of joining membersdisposed at substantially equal intervals thereon above said insulatingsurface, a plurality of needle electrodes being retained respectively bymeans of said joining members substantially vertical with reference tothe plane of said carrier member, releasing the retaining force of saidjoining members on said needle electrodes, whereby said needleelectrodes are caused to contact said insulating surface, the tips ofsaid needle electrodes forming an envelope which conforms to the shapeof the insulating surface reapplying the retaining force of said joiningmembers on said needle electrodes, separating said needle electrodes andsaid insulating surface a predetermined distance, and applying anelectric discharge potential to said needle electrodes whereby thecorona discharge emitted by said needle electrodes depositssubstantially uniformly on said insulating surface.
 5. The method as setforth in claim 1 wherein said insulating member comprises anelectrophotographic layer overlying a conductive substrate.
 6. Apparatusfor uniformly charging the surface of a curved insulating membercomprising: a carrier member having a plurality of joining membersdisposed at substantially equal intervals on said carrier member and aplurality of needle electrodes retained respectively by said joiningmembers substantially vertical with reference to the plane of saidcarrier member, said carrier member being positioned above saidinsulating surface, means for applying a force to said needle electrodesof sufficient magnitude to overcome the retaining force of said joiningmembers whereby said needle electrodes are caused to contact saidinsulating surface, the tips of said needle electrodes forming anenvelope which conforms to the shape of the insulating surface, meansfor separating said needle electrodes and said insulating surface apredetermined distance, and means for applying an electric dischargepotential to said needle electrodes, whereby the corona dischargeproduced by said needle electrodes deposits substantially uniformly onsaid insulating surface.
 7. The apparatus as set forth in claim 6wherein said insulating member comprises an electrophotographic layeroverlying a conductive substrate.
 8. The apparatus as set forth in claim6 further including an additional carrier member for supporting saidneedle electrodes, whereby said needle electrodes are maintainedsubstantially in parallelism.
 9. The apparatus as defined in claim 6further including means for shielding said needle electrodes from theeffect of the discharge produced by adjacent needle electrodes. 10.Apparatus for uniformly charging the surface of a curved insulatingmember comprising: a carrier member having a plurality of joiningmembers disposed at substantially equal intervals on said carrier memberand a plurality of needle electrodes retained respectively by saidjoining members substantially vertical with reference to the plane ofsaid carrier member, said cArrier member being positioned above saidinsulating surface, means for releasing the retaining force of saidjoining member on said needle electrodes whereby said needle electrodesare caused to contact said insulating surface, the tips of said needleelectrodes forming an envelope which conforms to the shape of theinsulating surface, means for reapplying the retaining force of saidjoining members on said needle electrodes, means for separating saidneedle electrodes and said insulating surface a predetermined distance,and means for applying an electric discharge potential to said needleelectrodes, whereby the corona discharge produced by said needleelectrodes deposits substantially uniformly on said insulating surface.11. The apparatus as set forth in claim 10 wherein said insulatingmember comprises an electrophotographic layer overlying a conductivesubstrate.
 12. The apparatus as set forth in claim 10 further includingan additional carrier member for supporting said needle electrodes,whereby said needle electrodes are maintained substantially inparallelism.
 13. The apparatus as defined in claim 10 further includingmeans for shielding said needle electrodes from the effect of thedischarge produced by adjacent needle electrodes.